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<h1>Space Shuttle ascent autopilot</h1>
<p><i>To see this help page during the simulation session, after launching the scenario press Alt-F1.</i></p>
<p>The default Space Shuttle Atlantis bundled with Orbiter now contains a built-in ascent autopilot.</p>
<p>You can set it up via the <i>Ascent AP</i> MFD mode: After starting this scenario, switch to cockpit mode (<b>F1</b>), call up the mode selection screen for the left MFD (<b>LShift-F1</b>), and select the Ascent AP mode (<b>LShift-B</b>).</p>
<p>The MFD display shows the commanded launch azimuth angle, initially set to 90&deg; (east), the resulting orbit inclination, and the commanded orbit altitude after circularisation, initially set to 350km.</p>
<p>You can change the launch azimuth angle by pressing the <b>AZ-</b> and <b>AZ+</b> MFD buttons. The final orbit inclination will be automatically recalculated. You can change the target orbit altitude by pressing the <b>AL-</b> and <b>AL+</b> MFD buttons.</p>
<p>For intercepting the International Space Station you will have to set the launch azimuth so that the orbit inclination matches that of the ISS. With the ISS orbit inclination of 51.6&deg; this will typically result in a launch azimuth of 43&deg; or 137&deg;, depending on whether the ISS is intercepted at the ascending or descending section of its orbit.</p>
<p>Note that the autopilot does not check if the commanded target orbit can be achieved. If you select an orbit with too high altitude or a launch azimuth too far from 90&deg; the autopilot will try to follow the target trajectory until it runs out of fuel.</p>
<p>After setting the launch parameters, wait for the desired launch window (e.g. until the ISS groundtrack crosses the launch site), and press the <b>L</b> MFD button to launch.</p>
<p>The autopilot will drive the gimbal angles for the Solid Rocket Boosters (SRB) and Space Shuttle Main Engines (SSME) to provide the required roll and pitch profiles.</p>
<p>The SRBs will be jettisoned when spent, as well as the external tank (ET) after main engine cut-off (MECO).</p>
<p>If the apogee altitude at MECO is lower than the commanded orbit altitude, the autopilot will initiate a first burn of the Orbital Maneuvering System engines (OMS-1), otherwise the OMS-1 burn is skipped.</p>
<p>At apogee, a second (or only) OMS burn is initiated (OMS-2) which will raise the perigee altitude to the commanded orbit altitude, and circularise the orbit.</p>
<p>After the OMS-2 burn, the autopilot will deactivate itself.</p>
<p>From launch until MECO, you can monitor the gimbal angles of the SRB and SSME engines visually on the second page of the Ascent AP MFD screen: Press MFD buttons <b>PG-</b> and <b>PG+</b> to switch between the pages of the Ascent AP mode.</p>
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